From the Rigveda
ॐ भूर्भुवः स्वः । तत्सवितुर्वरेण्यं भर्गो देवस्य धीमहि धियो यो नः प्रचोदयात्
oṁ bhūr bhuvaḥ svaḥ · tat savitur vareṇyaṁ bhargo devasya dhīmahi dhiyo yo naḥ pracodayāt

“We hold in mind the radiant light of the life-giving sun. May it brighten our thinking.”

The Gayatri · Rigveda 3.62.10
In plain terms

The tradition's most recited verse. It asks for one thing: that the same light which drives the sun might brighten human thinking. Three lines of eight syllables; even its shape is counted.

It is a request for clear thought before it is anything else, which is why it has opened studies and mornings for so long. Traditionally received at initiation, it is set down here for understanding, the way this site sets down everything.

All the verses, by the moment you need them